Shakashaka is a pencil-and-paper puzzle proposed by Guten and popularized by
the Japanese publisher Nikoli (like Sudoku). We determine the computational
complexity by proving that Shakashaka is NP-complete, and furthermore that
counting the number of solutions if #P-complete. Next we formulate
Shakashaka as an integer programming (IP) problem, and show that an IP solver
can solve every instance from Nikoli's website within a second.